White Peach Scale, Pseudaulacaspis pentagona (Targioni-Tozzetti)

I. Introduction: The white peach scale (WPS) is a native of the Orient that was introduced into Georgia in the late 1800's. In the U.S. it is primarily a pest in the deep South, but has also occurred in southern Virginia.  A related scale, white prunicola scale (Pseudaulacaspis prunicola (Maskell)) also infests peach.  It was formerly included with white peach scale, but occurs in more northern parts of the range (NY, etc.).  But there is broad overlap in both host and geographic range; both occur on Prunus (and other genera) in VA, WV and MD.  The best way to differentiate is in slide-mounted specimens.  The spines on the edge of the last abdominal segment are forked in WPS, and simple in white prunicola scale (Kosztarab 1996).

II. Hosts: It is most common on peach, but will also attack other stone fruits. It feeds on several hundred other plant species, including privet, mulberry, chinaberry, and flowering cherry.

III. Description: The adult female is a creamy-white to reddish-orange sac-like insect about 4/100 inch (1 mm) in diameter. Each female is covered by a waxy scale that is oval to circular, grayish to brownish-white, and 1/10 inch (2-2.5 mm) in diameter. The adult male is a tiny, yellow, two-winged insect <4/100 inch (<1 mm) long. Immature males are covered with an elongate, snowy white scale about 6/100 inch (1.5 mm) long. Eggs, which are laid underneath the scale covering, are orange (females) or pink (males). Nymphs (crawlers) are tiny, oval, and white to orange with six legs.

IV. Biology: WPS overwinters on the tree as a fertilized female beneath the scale covering. Beginning at the petal fall stage of peach, each female lays 100-150 eggs over a one month period, with hatch occurring in about 10 days. Following egg hatch, crawlers immediately leave the scale covering and move to new sites to begin feeding on the bark. In about a week after settling down to feed, crawlers begin forming a scale covering. Male scales cluster in large numbers on the trunk and scaffold limbs so as to completely cover the bark and give the tree a "whitewashed" appearance. Female scales tend to disperse throughout the tree, but are seldom seen on terminal, green wood. Females remain under the scale covering throughout their life. Males develop wings when mature, emerge from their scale covering, and seek out and mate with females. There are 3 generations per year in Virginia, with second and third generation crawlers present in July and from late August through September, respectively.

V. Injury: Scale feeding removes sap from the tree which reduces vigor. Foliage of infested trees may become sparse and yellow. Fruit size may be reduced and premature drop is likely to occur, especially f scale feeding is accompanied by other stress. Heavy infestations can result in the death of twigs, branches, and even trees if left unattended for 2 to 3 years.

VI. Monitoring: Monitor crawler emergence with black electrician's tape wrapped around scale infested branches with the sticky side out. A thin coating of petroleum jelly will enhance and extend the tape's effectiveness in capturing crawlers. Monitoring should be conducted after harvest to detect the third generation. There are no thresholds for WPS.

Additional References:
Kosztarab, M. 1996.  Scale Insects of Northeastern North America: Identification, Biology and Distribution.  Va. Museum Nat. Hist.  Spec. Pub. No. 3.  650 p.

This is taken primarily from a chapter by H. W. Hogmire and D. F. Polk on peach indirect pests, reprinted with permission from Mid-Atlantic Orchard Monitoring Guide, published by NRAES, 152 Riley-Robb Hall, Ithaca, New York 14853-5701. (607) 255-7654.
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